Operators of hazardous equipment are subjected to many dangers from the equipment they operate. Various safety devices have been used to try and protect the operator and others from the hazardous equipment. Electrosensitive protection equipment is widely used in industrial settings to protect operators of hazardous equipment from injury. Such devices consist of a sensing function, a control or monitoring function, and an output signal switching device. The sensing function collects data from a defined safety zone surrounding the dangerous equipment. The safety zone may be a line, an area or volume, depending on the sensing technology used. When the control function determines that the sensor data provided by the sensing function corresponds to an intrusion into the safety zone, an output signal is produced that may either sound an alarm or deactivate the hazardous equipment.
A variety of electrosensitive protection equipment is commercially available, including single beam photodetectors. This type of device uses a light source and detector and provides access monitoring. Interruption of the beam due to crossing the line between the source and detector triggers a safety violation. A light curtain consists of an array of emitter/detector pairs. They are normally mounted in a pair of enclosures monitoring a vertical plane between the enclosures providing access monitoring of the penetration of a rectangular plane. Further devices comprise laser scanners, safety mats and safety cameras. A safety camera uses images obtained from a video camera to detect intrusion into the safety zone. It provides both access and presence monitoring by separately analyzing the border of the safety zone and the interior of the safety zone.
Current electrosensitve protection equipment is designed to prevent injury by deactivating potentially hazardous equipment whenever any object enters the monitored safety zone. This means that the equipment is disabled while the operator is present in the safety zone and it cannot perform other tasks. In many applications it is necessary for both human operators and automated equipment to have access to a shared work area, such as for loading and unloading of material. In some instances, a muting function is included to temporarily disable the safety function while the machine or material enters the safety zone. This is typically used in conveyor application where it is desirable to admit material carried by the conveyor but still exclude human intrusion. It normally requires the use of additional sensors that can distinguish between humans and the admitted material on the basis of size or velocity.
There is a need for a safety mechanism that protects the operator and others from hazardous equipment. There is a need for such a system that does not interfere with the normal operation of the equipment. There is yet a further need for a safety mechanism that allows safe shared access to a zone by both the machine and an operator.